An increase in internet traffic has led to a demand for larger capacity of trunk line optical communication systems, and optical receivers/transmitters capable of transmitting signals at a rate of over 100 Gbit/s per wavelength are being researched and developed. As a bit rate per wavelength increases, a deterioration in signal quality occurs due to a degradation in the optical signal noise ratio (OSNR) tolerance, wavelength dispersion in a transmission path, or a waveform distortion caused by polarization mode dispersion or nonlinear effects.
Related arts are disclosed in Japanese Laid-open Patent Publication No. 2011-015013.